The present invention is directed to the field of ophthalmic surgery. More specifically, the invention is directed to a lubricating solution that may be utilized during various ophthalmic procedures, but is particularly useful in facilitating the formation of a corneal flap during laser in situ keratomileusis (“LASIK”).
LASIK surgery involves the use of a microkeratome to make an incision in the cornea transverse to the optical axis. This incision results in the formation of a corneal flap which is temporarily lifted and folded back so as to expose underlying tissue which is then sculpted or ablated with a laser so as to modify the curvature of the cornea and thereby correct the vision of the patient. For further background regarding LASIK surgery, particularly the formation of the corneal flap by means of a microkeratome, please refer to the following publications:
Pallikaris et al., “Laser In-Situ Keratomileusis”, Lasers in Surgery and Medicine, volume 10, Pages 463-468 (1990);
Carr et al., “Laser In-Situ Keratomileusis”, Ophthalmology Clinics of North America volume 10, pages 533-543 (1997);
Gimbel et al., “Indications, Results, and Complications of LASIK”, Current Opinion in Ophthalmology, volume 9, pages 3-8 (1998);
Farah et al., “Laser In-Situ Keratomileusis: Literature Review of a Developing Technique” Journal of Cataract and Refractive Surgery, volume 24, pages 1059-1063 (1998); and
Wilson, “LASIK Surgery”, AORN Journal, volume 71, pages 963-983 (2000).
Although the LASIK surgical procedure has now been conducted on thousands of patients, certain aspects of the procedure occasionally give rise to complications. The formation of the corneal flap is one aspect of the overall LASIK procedure which can give rise to complications. Specifically, the formation of the corneal flap can result in epithelial abrasions or other damage due to the microkeratome blade, and the cut or incision by means of the microkeratome blade can sometimes be somewhat unpredictable. Moreover, in some patients, corneal haze or edema subsequent to surgery and flap wrinkles or curled flap edges have been attributed to problems in forming the corneal flap with the microkeratome. The failure of the flap to reseal following surgery is also a significant complication, because such failure creates a greater risk of infection and may adversely affect visual acuity.
In view of the foregoing, there is a need for products which will enhance the ability of surgeons to form the corneal flap without damaging the cornea or associated ophthalmic tissues. In particular, there is a need for products which: (1) help to minimize corneal epithelial abrasions; (2) facilitate smooth, consistent cuts; and (3) expedite post-operative visual acuity by facilitating formation of a flap that is not wrinkled, fits well upon replacement and seals readily following the LASIK procedure.
Various types of solutions are currently being applied to the cornea prior to use of the microkeratome to form the corneal flap in LASIK surgical procedures. However, none of these solutions has been designed to meet the needs of the ophthalmic surgeon in conjunction with LASIK surgery. Consequently, each of these solutions has one or more drawbacks. For example, some of the solutions provide at least minimal lubrication, but contain other ingredients (e.g., antimicrobial preservatives) which are potentially toxic to the cornea and therefore highly undesirable in conjunction with an invasive surgical procedure such as LASIK surgery. Thus, the solutions currently being utilized are, at best, less than ideal.
The prior solutions have also created a problem with respect to the surgical devices utilized in the LASIK procedure. Specifically, the balanced salt solutions and other electrolyte-containing solutions which have been used to lubricate the cornea prior to formation of the corneal flap with a microkeratome contain relatively high concentrations of sodium chloride and other salts. The microkeratome is a very delicate, precise surgical instrument that includes a small motor and a gear-driven blade. The effectiveness and accuracy of the microkeratome in forming the corneal flap is directly dependent on the motor and gears. It has been found that the electrolyte solutions can create a corrosion or gumming problem on the motor and/or gears of the microkeratome and thereby interfere with its performance. Thus, there is a need not only for a lubricant solution which enhances the ability of the surgeon to form the corneal flap, but also for a solution which does not have any negative effects on the performance of the microkeratome.